Abstract: Effect of long term posting fertilization on components and regular changes of phosphorus in chao soil was studied in Tianjin during 1979-1993.Results showed that inorganic phosphorus was predominant,in which Ca P occupied the largest percentage,O P was second and only small part was the Al P and Fe P.Long term posting fertilization could significantly influence both the content of soil available P and the range of its changes.The effects of chemical phosphorus were more obvious than those of organic sources.The increasing and decreasing of soil available P depended heavily on whether chemical phosphorus was applied or not ,soil available P increased or decreased at the rate oF₁ mg/kg when P 45kg/ha was removed or P 28kg/ha was added.In addition,study also suggested that the changes of soil available P differed with the periods of experiment at time.Soil available P changed largely in the first two years,and the changes became smaller in the later 6-8 years,finally it remained in a normal value with quite small changes.Soil phosphorus could be balanced in 14 years when 18kg/ha year P₂O₅ was applied per 100 kg of grain yield under the wheat corn cropping system with the grain yield oF ₁1198kg/ha in total.

Key words: Long term posting fertilization, Chao soil, Change regularity of phosphorus

CLC Number: 

• S153